3qlp
From Proteopedia
X-ray structure of the complex between human alpha thrombin and a modified thrombin binding aptamer (mTBA)
Structural highlights
Disease[THRB_HUMAN] Defects in F2 are the cause of factor II deficiency (FA2D) [MIM:613679]. It is a very rare blood coagulation disorder characterized by mucocutaneous bleeding symptoms. The severity of the bleeding manifestations correlates with blood factor II levels.[1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12] Genetic variations in F2 may be a cause of susceptibility to ischemic stroke (ISCHSTR) [MIM:601367]; also known as cerebrovascular accident or cerebral infarction. A stroke is an acute neurologic event leading to death of neural tissue of the brain and resulting in loss of motor, sensory and/or cognitive function. Ischemic strokes, resulting from vascular occlusion, is considered to be a highly complex disease consisting of a group of heterogeneous disorders with multiple genetic and environmental risk factors.[13] Defects in F2 are the cause of thrombophilia due to thrombin defect (THPH1) [MIM:188050]. It is a multifactorial disorder of hemostasis characterized by abnormal platelet aggregation in response to various agents and recurrent thrombi formation. Note=A common genetic variation in the 3-prime untranslated region of the prothrombin gene is associated with elevated plasma prothrombin levels and an increased risk of venous thrombosis. Defects in F2 are associated with susceptibility to pregnancy loss, recurrent, type 2 (RPRGL2) [MIM:614390]. A common complication of pregnancy, resulting in spontaneous abortion before the fetus has reached viability. The term includes all miscarriages from the time of conception until 24 weeks of gestation. Recurrent pregnancy loss is defined as 3 or more consecutive spontaneous abortions.[14] Function[THRB_HUMAN] Thrombin, which cleaves bonds after Arg and Lys, converts fibrinogen to fibrin and activates factors V, VII, VIII, XIII, and, in complex with thrombomodulin, protein C. Functions in blood homeostasis, inflammation and wound healing.[15] Publication Abstract from PubMedAptamers are structured oligonucleotides that recognize molecular targets and can function as direct protein inhibitors. The best-known example is the thrombin-binding aptamer, TBA, a single-stranded 15-mer DNA that inhibits the activity of thrombin, the key enzyme of coagulation cascade. TBA folds as a G-quadruplex structure, as proved by its NMR structure. The X-ray structure of the complex between TBA and human alpha-thrombin was solved at 2.9-A resolution, but did not provide details of the aptamer conformation and the interactions with the protein molecule. TBA is rapidly processed by nucleases. To improve the properties of TBA, a number of modified analogs have been produced. In particular, a modified TBA containing a 5'-5' polarity inversion site, mTBA, has higher stability and higher affinity toward thrombin with respect to TBA, although it has a lower inhibitory activity. We present the crystal structure of the thrombin-mTBA complex at 2.15-A resolution; the resulting model eventually provides a clear picture of thrombin-aptamers interaction, and also highlights the structural bases of the different properties of TBA and mTBA. Our findings open the way for a rational design of modified aptamers with improved potency as anticoagulant drugs. Thrombin-aptamer recognition: a revealed ambiguity.,Russo Krauss I, Merlino A, Giancola C, Randazzo A, Mazzarella L, Sica F Nucleic Acids Res. 2011 Sep 1;39(17):7858-67. Epub 2011 Jun 28. PMID:21715374[16] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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